add git fsck to cronner, and UI for repository repair (not yet wired up)

Logs/FsckResults.hs

@@ -0,0 +1,43 @@
+{- git-annex fsck results log files
+ -
+ - Copyright 2013 Joey Hess <joey@kitenet.net>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+module Logs.FsckResults (
+	writeFsckResults,
+	readFsckResults
+) where
+
+import Common.Annex
+import Utility.Tmp
+import Git.Fsck
+import Git.Types
+
+import qualified Data.Set as S
+
+writeFsckResults :: UUID -> FsckResults -> Annex ()
+writeFsckResults u fsckresults = do
+	logfile <- fromRepo $ gitAnnexFsckResultsLog u
+	liftIO $ 
+		case fsckresults of
+			Nothing -> store S.empty logfile
+			Just s
+				| S.null s -> nukeFile logfile
+				| otherwise -> store s logfile
+  where
+  	store s logfile = do 
+		createDirectoryIfMissing True (parentDir logfile)
+		liftIO $ viaTmp writeFile logfile $ serialize s
+	serialize = unlines . map show . S.toList
+
+readFsckResults :: UUID -> Annex FsckResults
+readFsckResults u = do
+	logfile <- fromRepo $ gitAnnexFsckResultsLog u
+	liftIO $ catchDefaultIO (Just S.empty) $
+		deserialize <$> readFile logfile
+  where
+	deserialize l = 
+		let s = S.fromList $ map Ref $ lines l
+		in if S.null s then Nothing else Just s